458 THE IRON" INDUSTEY.
The Marquette ores are magnetites and hard and soft hematites, and are rich in iron. The ores from the Menominee and Gogebic ranges in Michigan and Wisconsin are hematites, and are very desirable as being in porous lumps and easily smelted. The Vermilion ores are very rich hematites; the softer kinds are low in phosphorus, while the deposits that furnish the massive hard lumps generally run considerably above the Bessemer limit. The Mesabi beds, for the most part, are mined with a steam shovel, as large areas lie near the surface. It is economical, however, to first loosen the ground by explosives. The ores are usually very fine, like sand, and in some cases almost pulverulent. Different mines vary in character, some ore being of such a size that it can be used alone in a blast furnace, while other beds are so fine and dusty that the average furnace manager will not use over 20 per cent. The composition of the ore, not only in the Mesabi districts but elsewhere, varies considerably, and constant vigilance is necessary to insure the separation of the "Bessemer" from the "non-Bessemer," by which terms are meant those portions which will give a pig-iron running below 0.10 per cent, in phosphorus, and those which will give an iron above that limit. The non-Bessemer was formerly more _or less of a drug in the market, but the development of the basic open-hearth furnace has furnished an outlet for this off-grade iron.
The fine condition of many Mesabi ores prevents their being employed alone in the blast furnace, and it is usually necessary to mix. with them a certain proportion of the "old range" ores. This renders it possible for the old mines to sell their product at a higher price, and thereby cover their greater cost. The percentage of Mesabi ores used in the furnace mixture is higher than formerly, from two causes: first, that furnacemen are learning how to use them, and are becoming accustomed to slips and scaffolds; and second, that many mines recently opened give a product of much coarser nature. The effect is seen in a relatively increasing price for these ores. The "Mesabi differential" for Bessemer ores was only 25 cents in 1905, while it was $1.10 in 1902. On non-Bessemer ores it was 20 cents in 1905, against 63 cents in 1902.
In regard to the relative amounts of the two kinds of ores I quote D. B. Woodbridge, in The Iron Age, January 3,1901:
"The fancy Bessemer ores of the older ranges, excepting the